apollo-server/packages/apollo-server-core/src/logging.ts

import { GraphQLExtension, GraphQLResponse } from 'graphql-extensions';
import { print, DocumentNode } from 'graphql';

export enum LogAction {
  request,
  parse,
  validation,
  execute,
  setup,
  cleanup,
}

export enum LogStep {
  start,
  end,
  status,
}

export interface LogMessage {
  action: LogAction;
  step: LogStep;
  key?: string;
  data?: any;
}

export interface LogFunction {
  (message: LogMessage);
}

// A GraphQLExtension that implements the existing logFunction interface. Note
// that now that custom extensions are supported, you may just want to do your
// logging as a GraphQLExtension rather than write a LogFunction.

export class LogFunctionExtension<TContext = any>
  implements GraphQLExtension<TContext> {
  private logFunction: LogFunction;
  public constructor(logFunction: LogFunction) {
    this.logFunction = logFunction;
  }

  public requestDidStart(options: {
    request: Request;
    queryString?: string;
    parsedQuery?: DocumentNode;
    operationName?: string;
    variables?: { [key: string]: any };
  }) {
    this.logFunction({ action: LogAction.request, step: LogStep.start });
    const loggedQuery = options.queryString || print(options.parsedQuery);
    this.logFunction({
      action: LogAction.request,
      step: LogStep.status,
      key: 'query',
      data: loggedQuery,
    });
    this.logFunction({
      action: LogAction.request,
      step: LogStep.status,
      key: 'variables',
      data: options.variables,
    });
    this.logFunction({
      action: LogAction.request,
      step: LogStep.status,
      key: 'operationName',
      data: options.operationName,
    });

    return (...errors: Array<Error>) => {
      // If there are no errors, we log in willSendResponse instead.
      if (errors.length) {
        this.logFunction({ action: LogAction.request, step: LogStep.end });
      }
    };
  }

  public parsingDidStart() {
    this.logFunction({ action: LogAction.parse, step: LogStep.start });
    return () => {
      this.logFunction({ action: LogAction.parse, step: LogStep.end });
    };
  }

  public validationDidStart() {
    this.logFunction({ action: LogAction.validation, step: LogStep.start });
    return () => {
      this.logFunction({ action: LogAction.validation, step: LogStep.end });
    };
  }

  public executionDidStart() {
    this.logFunction({ action: LogAction.execute, step: LogStep.start });
    return () => {
      this.logFunction({ action: LogAction.execute, step: LogStep.end });
    };
  }

  public willSendResponse(o: { graphqlResponse: GraphQLResponse }) {
    this.logFunction({
      action: LogAction.request,
      step: LogStep.end,
      key: 'response',
      data: o.graphqlResponse,
    });
  }
}